1. FIELD OF THE INVENTION
The present invention relates to a composition useful for preventing formation of resinous or pitch deposits and more particularly to a composition for preventing formation and separation of resinous or pitch deposits in the manufacture of paper, cardboard, boxboard, and the like cellulosic material, and to a process of preventing formation and separation of such resinous or pitch deposits.
2. DESCRIPTION OF THE PRIOR ART
The formation of resinous precipitates and deposits, i.e. of so-called pitch deposits presents a problem of considerable importance in the paper industry. These difficulties are caused by the presence of resins in the paper pulp or mechanical wood pulp and the like cellulosic raw materials. Resinous deposits originate also from residual sizing material which has not been completely utilized in paper sizing. The resinous materials coagulate and more deposited on and incrustate the pipelines and the walls of the stock preparation plants and vats and the screen, felts, presses, and drying cylinders of the paper machines. Precipitation of the resinous material results in soiling and in rendering sticky the apparatus used, in inhibiting the removal of water from the cellulosic material, in the formation of stains and pitch spots on the paper, and frequently in tearing and breaking of the paper resulting in faulty manufacture and defective final products and thus in production breakdown and losses.
Attempts have been made to overcome these difficulties by adding to the cellulose or paper pulp absorbents such as, for instance, kaolin or china clay. Addition of such absorbents decreases the stickiness of the precipitation resinous impurities or pitch. But such addition does not prevent separation and deposition of the resinous materials as such apart from the fact that addition of kaolin is undesired in the manufacture of many types of paper.
Furthermore, attempts have also been made to add to the paper pulp alkali metal polyphosphates, the solution of which had been adjusted to a pH-value between a pH of about 5.0 and about 8.0 in order to achieve the same results. Such addition is disclosed, for instance, in German Pat. No. 740,833.
Finally, it has been tried to overcome the difficulties caused by the precipitation of resinous materials by means of finely divided magnesium silicates.
All these additives, however, are capable of preventing formation of resinous precipitates and pitch deposits to a certain extent only. They fail to work especially if the manufacturing conditions are exceptionally difficult, for instance, if the water is of inferior quality, for instance, of a high degree of hardness, has a high content of polyvalent cations, such as iron, manganese, and the like ions, or is contaminated by humic acids, or if the manufacture of paper, cardboard, and the like materials takes place at higher temperatures or at unusual pH ranges.